Banca de DEFESA: CINTIA LUANA PINHEIRO SANTOS

Novel polymorphisms of Lalba and OLR1 genes and their associations with milk production traits in buffaloes.

Buffaloes, Fat, Gene expression, Point mutation, Milk production.

Buffaloes play a notable economic, social and environmental role in the world. Their milk is the second most produced and has excellent nutritional composition. In the meantime, it is necessary to understand the genetic factors by searching for the mechanisms that can influence the productivity of production animals. Therefore, the objective was to investigate single nucleotide polymorphisms (SNPs) in protein and lipid metabolism genes to associate them with data on milk production in buffaloes from the Amazon region. For this purpose, blood samples were collected from 85 females belonging to a property in the municipality of Bujaru/PA. DNA extractions were performed using the phenolic method, followed by Polymerase Chain Reaction (PCR), Purification and Sequencing of the coding regions of the LALBA (833 bp) and OLR1 (750 bp) genes. The Nsite v. 1.0 Software investigated the possible binding sites to transcription factors in both genes. 5. Furthermore, for the LALBA gene, the mRNA from milk epithelial cells was extracted to determine the expression profile in seven haplotypes selected in the population. After editing and sequence alignments, fifteen SNPs were found in total, ten in the LALBA gene and five in the OLR1 gene. One SNP of the InDel type in the LALBA gene stood out. None of the fourteen SNPs detected showed a significant association with the average milk production of the population (P>0.05). Seven of the ten SNPs observed in LALBA showed allele frequencies of wild-type nucleotides greater than 0.5 with 90% in Hardy-Weinberg equilibrium (HWE), with SNP -42 (A>G) presenting a strong binding site for the transcription factor hepatocyte nuclear factor 3 (HNF3). Expression analysis showed that haplotypes 4 and 2 showed the highest expression levels compared to the others (P<0.05). Two of the four SNPs found in the OLR1 gene were of the transition type and the other two were of the transversion type, all with high wild-type nucleotide allele frequencies above 0.90 with 75% under EHW conditions. However, for the SNPs at positions -555 InDel (TAAA) and -720 (C>T) found in the LALBA gene, as well as the one at position -672 (A>T) in the OLR1 gene, it was revealed that the heterozygotes exhibited higher average milk production values compared to the homozygotes and may, therefore, be subject to selection in the population for increased milk volume production in both. Thus, both the higher levels of LALBA mRNA expression observed in buffalo milk in two different haplotypes and the presence of heterozygous individuals with higher milk production, especially the Indel found in LALBA -555 (TAAA) and the SNP in OLR1 -672 (A>T), were candidates due to the additional effect that new alleles carry, causing greater genetic variability within the herd. Therefore, they may be desirable characteristics to be fixed in the population. However, more approaches focused on the relationship between point mutations and expression levels in somatic cells of milk, together with other genes that may be influencing milk production levels, should be carried out to investigate whether these variants can be proven through the phenotypes of the animals.